DAMS AS EXPERIMENTAL MANIPULATIONS: SPATIAL AND TEMPORAL GRADIENTS IN RESERVOIRS AND IN FLOODPLAIN LAKES

Dams have long been recognized to influence thermal and sediment load characteristics of impounded streams, but they also offer experimental opportunities for study of reservoir gradients, advective processes, and of the effects of flooding on floodplain lakes. By their control of hydrological variation, dams provide real opportunities for examination of ecological and evolutionary processes that are otherwise difficult or impossible to examine experimentally. Hydrological control of inflows may give rise to within basin and between basin gradients that are independent of morphometric characteristics of reservoir basins or of advective influences. Flood control alters timing and frequency of floodplain inundation, giving rise to impacts ranging from life history alteration in floodplain organisms to alteration of biodiversity gradients relative to the dam.